Vapor generator



L. J. CULVER VAPOR GENERATOR July 8, 19 58 2 Sheets-Sheet 1 Filed Aug. 10 1955 INVENTOR lbw/4 w JAMES (/LI/ER United States Patent 2,842,104 Patented July 8, 1958 VAPOR GENERATOR Leonard James Culver, London, England, assignor to Foster Wheeler Corporation, New York, N. Y., a corporation of New York Application August 10, 1955, Serial No. 527,599 6 Claims. (Cl. 122-480) This invention relates to vapor generators and more particularly to a vapor generator having a superheater and means for controlling the flow of combustion gases 1 through said superheater.

Superheat may be controlled by the use of equipment such as spray or shell-and-tube desuperheaters or by the provision of two furnaces. These expedients increase the size of the plant and, where space is restricted as in marine installation, superheat control isobtained at the expense of access to superheater tubes or reliability or simplicity of design or vital parts.

The vapor generator in accordance with the present invention has a single combustion chamber with two laterally adjacent banks of steam generating tubes extending between a steam drum and one or more water drums. A superheater is arranged between the two banks and extends substantially from front to back of the boiler (i. e. parallel to the longitudinal axes of the drums). The outer bank, that is the bank remote from the combustion chamber is divided into upper and lower sections by a transverse bafile which extends diagonally upwardly towards the flue from about the level of the top of the superheater. The baflle continues from the bank into the flue so as to divide the flue into two gas passages one or each of which is controlled by a damper. The level to which the superheater extends is such that a substantial proportion of the furnace gases can be passed to the flue without giving up heat by convection to the superheater. I

By adjustment of the damper or dampers, the proportion of combustion gases flowing to the flue through the superheater or so as to by-pass the superheater can be regulated. In this Way, for any particular load the steam temperature can be varied closely throughout a wide range.

The baflie which divides the outer bank does not project substantially beyond the inner bank, that is, the bank immediately adjacent the combustion chamber. Consequently, it is not subjected to high temperatures and will require little, if any, maintenance.

The boiler in accordance with the invention need not be of larger dimensions than a single furnace boiler of comparable steam output having no provision for control of superheat.

As the baffle does not extend through the space between the two banks of tubes and the superheater extends substantially through that space, it is possible to accomplish removal of a defective superheater tube without removal of the entire superheater unit. Moreover, by leaving between the inner bank and the superheater, a space at least equal to the width of the superheater, it is possible to remove superheater tubes even if the space available between the boiler and the bulkhead or other partition is of substantially less width than the length of a tube.

The particular features and advantages which characterize the invention will be understood from the following description when considered in connection with the accompanying drawings forming a part thereof and in which:

Fig. 1 is a sectional view, in elevation, of the boiler according to this invention;

Fig. 2 is an enlarged fragmentary view of the batfle structure taken on the line 2-2 of Fig. 1;

Fig. 3 is a fragmentary view of a second embodiment of the baffle structure according to this invention;

Fig. 4 is a fragmentary view, similar to Fig. l, showing in detail the superheater structure with one tube supporting bracket removed; and

Fig. 5 is a'view similar to Fig. 4 showing a second embodiment of the superheater structure.

The boiler shown in Fig. 1 is a single furnace water tube marine boiler having a setting 10 comprising side walls 11 and 12, rear wall 13, front Wall (not shown), floor 14 and roof 15. A steam drum 16 in roof 15 is connected to a water drum 17 by two banks of boiler tubes 18 and 19 arranged between a furnace chamber 20 and a flue 21. Combustion gases are provided by burners 20A mounted in rear wall 13 of the setting 10.

The tube bank 19 remote from the furnace, hereinafter referred to as the outer bank, comprises a substantially greater number of tubes than bank 18 immediately adjacent furnace chamber 20, which bank will be hereinafter called the inner bank. A superheater 22 schematically shown in Fig. l, is arranged between the two banks 18 and 19. Supcrheater 22 is dispersed close to the outer bank 19 with a space 24 somewhat wider than superheater 22 betweensaid superheater and the inner bank 18.

As shown in Figs. 4 and 5 superheater 22 comprises U-shaped tubes 26 arranged one within another in nests of three lying in substantially horizontal planes, the open ends of the U-shaped tubes 26 extending outside the boiler into headers (not shown). Supcrheater 22 terminates at the base near the water drum 17 and at the top substantially short of the steam drum 16 thereby providing a passage for furnace gases which have passed through inner bank 18 to pass to the flue 21 without passing through the superheater 22.

At substantially the level of the top of the superheater 22, a bafiie 28 extends transversely of bank 19 and diagonally upwards to divide said outer bank into an upper and lower section. The bathe extends at an angle upwardly away from the superheater 22 normal to the tubes 19A of tube bank 19 so as to define with the ,of refractory orinsulating material incorporating any desired reinforcement such as wire or lugs welded to the tubes; or it may be formed of metal strips shaped so that strips can be inserted between the tube rows and so as to embrace the tubes.

Beyond the outer bank 19, the baflle 28 vertically extends into the flue 21 so as to provide two parallel gas passages 31 and 31A. Gas passage 31 communicates with passage 30. A damper 34 and a damper 34A are arranged across each of the passages 31 and 32, respectively. By adjustment of these dampers, the relative gas llow through the two passages 31 and 31A is variable.

In operation, with gas passage 31 above the battle 28 closed, as shown in Fig. ,l, the furnace gases pass .to the flue 21 through the superheater 22 and, therefore, the superheated steam is heated to a maximum temperatur By progressively closing damper 34A and opening damper 34, a progressively larger proportion of the combustion or furnace gases will be caused to by-pass the superheater 22 and the superheater steam temperature will be progressively lowered. Thus, for any particular load, the superheat temperature may :be varied by adjustment of the dampers 34 and 34A. The gas passages 30 and 31 are constructed so that a substantial proportion of combustion gases can .be passed therethrough whereby a wide range of superheater steam temperature adjustments are obtainable for any particular load.

A boiler, according to this invention, designed to produce steam at 850 F. over a wide range of loads, can be made to produce steam, when desired, at a tempcrature as low as 600 F., at any particular load. The invention also allows the boiler .to be given an inverted superheat characteristic, that is to say, to allow the steam temperature to.decrease with an increase of load. For instance, a steam temperature of 850 F., can be obtained up to 50% of load and a steam temperature of 750 F. above 50% of load by damper adjustment without prejudicing the ability of the boiler to produce steam .at 700 F. at all normal operating loads. The actual operating characteristics is dependent upon the relative proportion of heating surface in the two parallel gas paths.

The dampers 34 and 34A, being beyond the outer bank of boiler tubes 19A, are in a relatively cool zone and are not subject to deterioration. If desired, they can be arranged in a still cooler zone by extending the bafilc 28 through the flue 21 to a point beyond an economizer 35 or any other heat recovery device which may be disposed in line 21.

The baffie 28 does not extend substantially into the space between the banks of boiler tubes 18 and 19 so that it is not subjected to high temperature combustion gases.

Since the bafile 28 does not extend through the space between the two boiler tube banks 18 and 19, replacement of superheater tubes is simplified, as hereinafter explained.

As above described, the superheater 22 is made up of nests of three U-shaped tubes .26 lying one within another in the same plane. In the form of the invention shown in Fig. 4, the superheater is divided into a number of sections 23 one above the other, each comprising four superimposed nests of tubes. tubes 26 are connected to headers (not shown) outside the furnace. Near their bent ends, the tubes are supported in brackets 27, one to .each section 23 of superheater 22. Each bracket 27 is an angle plate fixed to the rear wall 13 of the boiler setting and having four horizontal slots 27A one above the other through which pass the three tubes 26 forming one of the four nests in a section. To replace a tube, bracket 27, in which the tube to be removed is supported, is detached from the rear wall 13 of the setting 10 by pulling .it outwards oil the bent ends of the tubes and through an access port (not shown) in the setting wall 13. After removal of the bracket 27, if the defective tube is the outermost tube in the nest, it is removed by detaching it from the headers; if it is the middle or innermost tube its removal can be similarly effected after removal of the outer tube or tubes. At the most, it is necessary to re move only three tubes.

The tubes 26 are removed by being pulled out of the setting 10 in the direction of their length. This,

The ends of U-shaped however, is feasible only if there is outside the boiler setting 10 a space of a width at least equal to the length of tubes 26. Where such a space does not exist, a defective tube can then be displaced sideways into space 24, until it is clear of the superheater 22, as shown in Fig. 4, thence turned about its longitudinal axis so that it lies in the vertical plane and then up-ended while being drawn out of the boiler. Replacement tube or tubes are placed in position in the superheater 22 by the reverse process.

As shown in the embodiment in Fig. 5, the tubes 26 are supported in a number of plates 29 having individual holes for the tubes 26 instead of slots, one such plate being provided for each section 23 of the superheater and the various plates 29 being arranged to stand one upon another in a vertical plane on a specially arranged water tube 36. The tubes 26, in this embodiment, can be withdrawn only if there is outside the boiler a space at least equal to the length of tubes 26.

Also, the superheater may, if desired, be arranged so as to provide a bypass passage round its lower end as well as round its upper end. Three parallel gas passages would then be formed, the two outer passages being provided with.dampers.

On the side remote from the furnace the inner bank may, if desired, be provided with a short battle wall which induces an upward flow of gases from the furnace and thus assists, when the upper by-pass passage is open, in causing the gases to pass to the flue without going through the superheater.

The boiler in accordance with the invention may, if desired, have more than two banks of steam generating tubes. For example, a third bank can be arranged on the flue side of the outer bank and of the damper or dampers controlling the gas flow. In such a case, the boiler may have one, two or three water drums, as desired.

Although the invention has been disclosed as applied to the generation of steam, it is not limited thereto but is capable of application to the generation of vapors generally. j

From the foregoing" disclosure it will be understood that the present invention provides a boiler having very flexible control of the superheated steam temperature and that such is achieved without detracting from simplicity, reliability and accessibility of its parts. Also, the present invention permits removal of superheater tubes without requiring the removal of the entire superheater unit for replacement of a tube. The space provided between the superheater and the inner bank which permits tube replacement also facilitates inspection and cleaning of the superheater and the inner bank of boiler tubes.

What is claimed is:

l. A vapor generator comprising a setting having a furnace chamber therein, means for firing said furnace chamber thereby producing combustion gases, a combustion gas outlet in said setting, an upper liquid-vapor drum and a lower liquid drum disposed in said setting, an inner bank of vapor generating tubes, an outer bank of vapor generating tubes, said inner bank and said outer bank of tubes being laterally spaced from one another, the tubes of said banks communicating at their opposite ends with the two drums, said tubes extending substantially vertically within the setting at a location between the furnace chamber and the combustion gas Outlet, a superheater having U shaped tubes disposed in the space between the inner and outer vapor generating tube banks and spaced below said upper drum, said U-shaped superheater tubes being disposed one above the other with the longitudinal axes of the tubes extending substantially normal to the longitudinal axes of the tubes of the inner and outer banks of vapor generating tubes, said superheater spaced from one of said tube banks a distance slightly greater than the width of the largest U shaped superheater tubes to permit removal of said superheater tubes by lateral displacement thereof into the space between the superheater and said tube bank.

2. A vapor generator comprising a setting having a furnace chamber therein, means for firing said furnace chamber thereby producing combustion gases, a combustion gas outlet in said setting, an upper liquid-vapor drum and a lower liquid drum disposed in said setting, an inner bank of vapor generating tubes, an outer bank of vapor generating tubes, said inner bank and said outer bank of tubes being laterally spaced from one another, the tubes of said banks communicating at their opposite ends with the two drums, said tubes extending substantially vertically within the setting at a location between the furnace chamber and the combustion gas outlet, at superheater having U shaped tubes disposed in the space between the inner and outer vapor generating tube banks and spaced substantially below said upper drum, said U-shaped superheater tubes being disposed one above the other with the longitudinal axes of the tubes extending substantially normal to the longitudinal axes of the tubes of the inner and outer banks of vapor generating tubes, said superheater being spaced from one of said tube banks a distance slightly greater than the width of the largest U shaped superheater tubes to permit removal of said superheater tubes by lateral displacement thereof into the space between the superheater and said tube bank, baffle means extending transversely of the outer bank below said steam and water drum from adjacent the top of said superheater to said outlet thereby to de fine two combustion gas passageways, and means for controlling the amount of gas flow through said passageways thereby regulating the gas flow across the superheater.

3. A vapor generator comprising a setting having a furnace chamber therein, means for firing said furnace chamber thereby producing combustion gases, a combustion gas outlet in said setting, an upper liquid-vapor drum and a lower liquid drum disposed in said setting, an inner bank of vapor generating tubes, an outer bank of vapor generating tubes, said inner bank and said outer bank of tubes being laterally spaced from one another, the tubes of said banks communicating at their opposite ends with the two drums, said tubes extending substantially vertically within the setting between the furnace chamber and the combustion gas outlet, a superheater having U-shaped tubes disposed between and normal to the inner and outer vapor generating tube banks and spaced substantially below said upper drum, said super-- heater being spaced from one of said banks a distance slightly greater than the width of the largest U-shaped tubes to permit removal of said superheater tubes by lateral displacement thereof into the space between the superheater and said tube bank, a baffle extending normal to the tubes of the outer tube bank from the top of said superheater to said outlet at an angle inclined with respect to a horizontal plane and extending transversely of the setting to define two combustion gas passageways, said bafile consisting of a plurality of abutting plates each secured to a tube of the outer tube bank so as to lie in the same plane, and means for controlling the quantity of gas flow through said passageways thereby regulating the gas flow across the superheater.

4. A vapor generator comprising a setting having a furnace chamber therein, means for firing said furnace chamber thereby producing combustion gases, a combustion gas outlet in said setting, an upper liquid-vapor drum and a lower liquid drum disposed in said setting, an inner bank of vapor generating tubes, an outer bank of vapor generating tubes, said inner bank and said outer bank of tubes being laterally spaced from one another,

the tubes of said banks communicating at their opposite ends with the two drums, said tubes extending substantially vertically within the setting between the furnace chamber and the said gas outlet, a superheater disposed between the inner and outer vapor generating tube banks and spaced substantially below said upper drum, said superheater comprising a plurality of sections arranged vertically one above the other, each of said sections comprising a plurality of nested U shaped tubes disposed horizontally in said setting, each nest of tubes being disposed one above the other within each section, said superheater sections being disposed in spaced relationship with one of said vapor generating tube banks a distance slightly greater than the width of the largest U-shaped tubes to permit removal of said superheater tubes by lateral displacement thereof into said space, baflle means extending transversely of the outer tube bank below said liquid-vapor drum from adjacent the top of said superheater, said outlet to thereby define two combustion gas passageways, and means in said passageways to control the amount of gas flow through the passageways, thereby regulating the gas flow over the superheater.

5. A vapor generator comprising a setting having a furnace chamber therein, firing means in said furnace chamber to thereby produce combustion gases, a combustion gas outlet insaid setting, an upper liquid-vapor drum and a lower liquid drum disposed in said setting, an inner bank of vapor generating tubes, an outer bank of vapor generating tubes, said inner bank and said outer bank of tubes being laterally spaced from one another, the tubes of said banks communicating at their opposite ends with the two drums, said tubes extending substantially vertically within the setting between the furnace chamber and the said gas outlet, a superheater disposed between the inner and outer vapor generating tube banks and spaced substantially below said upper drum, said superheater comprising a plurality of sections arranged vertically one above the other, each of said sections comprising a plurality of nested U shaped tubes disposed horizontally in said setting, each nest of tubes being disposed one above the other within each section, said superheater sections being disposed in spaced relationship with one of said vapor generating tube banks a distance slightly greater than the width of the largest U-shaped tubes to permit removal of said superheater tubes by lateral displacement thereof into said space, a bracket for each section removably mounted to the setting and adapted to support the tubes in each section, bafile means extending transversely of the outer tube bank below said liquid-vapor drum from adjacent the top of said superheater to said outlet to thereby define two combustion gas passageways, and means in said passageways to control the amount of gas flow through the passageways, thereby regulating the gas flow over the superheater.

6. The vapor generator of claim 5, wherein the bracket has a plurality of vertically spaced elongated openings corresponding in number to the number of nests of tubes in each superheater section and adapted to receive each nest of tubes therethrough, said bracket being mounted in the setting so as to support the tubes adjacent their U bend end portions.

References Cited in the file of this patent UNITED STATES PATENTS 1,835,263 Blanton Dec. 8, 1931 2,023,223 Gordon Dec. 3, 1935 2,024,569 Engler Dec. 17, 1935 2,332,534 Rooney Oct. 26, 1943 FOREIGN PATENTS 628,221 Great Britain Aug. 24, 1949 

